`The Shield' proves again the best really can get even better

As "The Shield" returns for a fifth season (9 p.m. Tuesday, FX), L.A. cop Mackey is in deep trouble, and for good reason.

For years, he has ruled Los Angeles' violent Farmington district as if its mean streets were his own personal kingdom. Doling out street justice on his own terms, by his own twisted rules, and protecting his posse, the Strike Team, were his top priorities. They were, at times, his only priorities.

Though his superiors have depended on Mackey -- and his questionable methods -- to get results in the past, as last season ended, the top brass of the police department started to ponder the idea of sacrificing Mackey in a corruption scandal. Hurt by budget cutbacks and a poor image among the public, the police brass are willing to do whatever it takes to clean up the department's image: That involves making Mackey their fall guy.

The thing is, Mackey has done many of the bad things he's suspected of (and has done even worse things that his bosses don't know about). So why do we spend the first few episodes of the fifth season on the edge of our seats, hoping that Mackey doesn't get snared in Internal Affairs' net?

It's partly because of Michael Chiklis' bravura performance as Mackey; even when he's not speaking, he's the charismatic focus of any scene. It's also because "The Shield," underneath all the cop politics, is an exploration of moral quandaries that resist easy answers. Quite often Mackey and his crew are the only thing keeping the streets of Farmington from total anarchy (though chaos is always present; in the first episode of the season, there are two violent riots, one at a funeral, another at a high school).

"The Shield" has much more than Chiklis going for it, though. Director D.J. Caruso does a terrific job of making the season-opener a visceral, action-packed thrill ride; the writing staff of the show is still in top form, and this year comes up with harrowing plots about human trafficking and dark intimations about the health of the hardworking but terminally tired Detective Claudette Wyms (C.C.H. Pounder).

Much of the weight of the first half of the season falls on Kenneth Johnson, who plays Strike Team member Curtis "Lem" Lemansky, who's a target of Internal Affairs and is forced to wear a wire to get information that will implicate Mackey in the murder of another cop. Johnson is more than up to the task of portraying Lem's tortured conscience. As is the case with the rest of the top-notch "Shield" cast, his performance is always subtle and believable.

Forest Whitaker, on the other hand, is a bit mannered and off in his first few appearances as Internal Affairs investigator Jon Kavanaugh, but he soon settles into a slightly more subtle groove. Still, he won't make anyone soon forget Glenn Close's virtuoso performance last season as Mackey's boss and adversary, Monica Rawling. It'd be great to see Close guest-star on the show again; she brought a wonderfully urgent fire to Rawling.

There are other new faces this season; a female rookie (Paula Garces) tries to learn the ropes, but finds Farmington cops are a tough lot to win over, and Laura Harring ("Mulholland Drive") is effective as a canny lawyer who sees through Mackey's self-serving bravado.

Many series feel as though they're just coasting going into their fifth seasons. "The Shield," already the best crime show on TV, feels as if it's just now getting to the best stuff.